[PATCH 6.6.y] net: fix NULL pointer dereference in l3mdev_l3_rcv

[PATCH 6.6.y] net: fix NULL pointer dereference in l3mdev_l3_rcv

[Rajani Kantha]

From: Wang Liang <wangliang74@huawei.com>

[ Upstream commit 0032c99e83b9ce6d5995d65900aa4b6ffb501cce ]

When delete l3s ipvlan:

    ip link del link eth0 ipvlan1 type ipvlan mode l3s

This may cause a null pointer dereference:

    Call trace:
     ip_rcv_finish+0x48/0xd0
     ip_rcv+0x5c/0x100
     __netif_receive_skb_one_core+0x64/0xb0
     __netif_receive_skb+0x20/0x80
     process_backlog+0xb4/0x204
     napi_poll+0xe8/0x294
     net_rx_action+0xd8/0x22c
     __do_softirq+0x12c/0x354

This is because l3mdev_l3_rcv() visit dev->l3mdev_ops after
ipvlan_l3s_unregister() assign the dev->l3mdev_ops to NULL. The process
like this:

    (CPU1)                     | (CPU2)
    l3mdev_l3_rcv()            |
      check dev->priv_flags:   |
        master = skb->dev;     |
                               |
                               | ipvlan_l3s_unregister()
                               |   set dev->priv_flags
                               |   dev->l3mdev_ops = NULL;
                               |
      visit master->l3mdev_ops |

To avoid this by do not set dev->l3mdev_ops when unregister l3s ipvlan.

Suggested-by: David Ahern <dsahern@kernel.org>
Fixes: c675e06a98a4 ("ipvlan: decouple l3s mode dependencies from other modes")
Signed-off-by: Wang Liang <wangliang74@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250321090353.1170545-1-wangliang74@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Rajani Kantha <681739313@139.com>
---
 drivers/net/ipvlan/ipvlan_l3s.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/ipvlan/ipvlan_l3s.c b/drivers/net/ipvlan/ipvlan_l3s.c
index d5b05e803219..ca35a50bb640 100644
--- a/drivers/net/ipvlan/ipvlan_l3s.c
+++ b/drivers/net/ipvlan/ipvlan_l3s.c
@@ -224,5 +224,4 @@ void ipvlan_l3s_unregister(struct ipvl_port *port)
 
 	dev->priv_flags &= ~IFF_L3MDEV_RX_HANDLER;
 	ipvlan_unregister_nf_hook(read_pnet(&port->pnet));
-	dev->l3mdev_ops = NULL;
 }
-- 
2.17.1

Re: [PATCH 6.6.y] net: fix NULL pointer dereference in l3mdev_l3_rcv

[Sasha Levin]

Subject: net: fix NULL pointer dereference in l3mdev_l3_rcv

Thanks!